\setuplist[chapter][pageconversionset=pagenumber]
\startstructureblockenvironmentstartsectionblockenvironment[frontpart]
\setupuserpagenumber[numberconversion=romannumerals]
\setuppagenumber[number=1]
\stopstructureblockenvironmentstopsectionblockenvironment
\startstructureblockenvironmentstartsectionblockenvironment[bodypart]
\setuppagenumber[number=1]
\stopstructureblockenvironmentstopsectionblockenvironment
</texcode>